Bushing assemblies are widely used in vehicular transportation such as joints in automobile suspension assemblies. One concern in automobiles is the reduction of vibrations induced from the road surface and isolation of the passenger compartment from such vibrations. Such vibrations may comprise a range of amplitudes and frequencies and motions in various directions. Automotive suspension systems are designed to reduce such vibrations. A front-end suspension system is typically made up of components including various arms, rods, links, etc. intermediate of the frame and the wheel assembly of the car. Generally, an elongated arm extends from the wheel assembly and another arm extends from the frame, the arms connected together at a connecting joint having a bushing assembly.
A common type of vibration-damping bushing assembly is the fluid-filled, rubber bushing assembly. Such bushing assemblies comprise a rubber core at least partially surrounded by a metal cylinder. The core includes fluid chambers which are fluidly isolated from each other about the exterior surface of the metal cylinder by sealing elements. A fluid-channel member positioned over the metal cylinder has channels to permit a damping fluid to pass from one fluid chamber to the other in response to changes in the axial or radial load on the bushing. A housing surrounds and captures the foregoing elements in a fluid-sealed manner to prevent leakage of the damping fluid therefrom.
The above-described bushing assembly is conventionally manufactured by molding, in a single step, the rubber core, metal cylinder, and sealing elements so that the same are vulcanized into a unitary assembly. Following this molding step, the outer diameter of the metal cylinder is decreased by calibration or swedging to relieve internal stress in the bushing material.